Molding apparatus

ABSTRACT

Method and apparatus for molding plastic articles by forming a parison on a core within an injection mold, cooling the exposed surfaces of the parison by heat transfer through the core and the mold, transferring said core to a delay position and permitting the redistribution of heat throughout the parison, and subsequently transferring said core to a mold for expanding the parison to the desired configuration. The apparatus comprises two sets of cores, each actuated by rotating and reciprocating means whereby one set of cores is located at a delay station while a parison and the finished article are formed on the other set of cores, the multiple core sets permitting the maintenance of maximum production rates, and maximum orientation of the finished article.

United States Patent 1191 Zavasnik MOLDING APPARATUS [75] Inventor: FredJ. Zavasnik, Bolingbrook, Ill.

{73] Assignee: Continental Can Company, Inc.,

New York, NY.

22 Filed: Dec. 16, 1971 21 App]. No.: 208,740

[52] US. Cl.425/242, 425/DIG. 209, 425/DlG. 211,

[51] Int. Cl B29d 23/03 [58] Field of Search 425/326, 387, 451, 249,324, 425/DlG. 205, DIG. 209, DIG. 211, 387 B,

14 1 Feb. 19,1974

Primary ExaminerRichard B. Lazarus Attorney, Agent, or Firm-Diller,Brown, Ramik & Wight [57] ABSTRACT Method and apparatus for moldingplastic articles by forming a parison on a core within an injectionmold, cooling the exposed surfaces of the parison by heat transferthrough the core and the mold, transferring said core to a delayposition and permitting the redistribution of heat throughout theparison, and subsequently transferring said core to a mold for expandingthe parison to the desired configuration. The apparatus comprises twosets of cores, each actuated by rotating and reciprocating means wherebyone set of cores is located at a delay station while a parison and thefinished article are formed on the other set of cores, the multiple coresets permitting the maintenance of maximum production rates, and maximumorientation of the finished article.

10 Claims, 5 Drawing Figures MOLDING APPARATUS BACKGROUND OF THEINVENTION This invention relates to the field of injection blow molding.More specifically, it relates to apparatus which may be utilized tomanufacture hollow articles of thermoplastic material and isparticularly adapted for use in conjunction with the injection blow moldprocess of my copending application, Ser. No. 201,823 filed Nov. 24,I971 and assigned to the same assignee as the instant invention. Thisprocess is intended to maximize the degree of orientation of themolecular chains of a plastic material so as to obtain hollow articleshaving high strength and resistance to deformation under highertemperatures and pressures. The process obtains such orientation byinjecting a thermoplastic material into a mold about a core and rapidlycooling those surfaces exposed to the core and the mold. Subsequently,the parison is transferred to a delay station whereby heat within theparison is permitted to flow to these surfaces, thus reducing thetemperature of the interior of the parison and reheating the exposedwalls so as to obtain a parison having a more uniform cross-sectionaltemperature within a range necessary to achieve biaxial orientation.When the desired temperature is obtained, the parison is expanded intothe desired configuration.

The instant invention proposes structure for performing this process ina most economical and efficient manner.

SUMMARY OF THE INVENTION Such structure includes injection and expansionmolds preferably disposed opposite one another, with a shaft disposedbetween them and carrying two sets of cores which are capable of bothreciprocable and rotatable movement. Such an arrangement permitsalternative movement of each set of cores between the molds and a delaystation necessary to achieve the more uniform parison temperature.

Accordingly, it is a primary object of my invention to provide anapparatus with which a biaxially oriented plastic article can bemanufactured at a high rate of production. Too, such apparatus isespecially adapted for uniformly reducing the temperature of a parisonfrom its injection temperature to its glass transition temperature so asto achieve a highly oriented plastic article such as a container forcarbonated beverages.

Additionally, it is an object of my invention to provide a moldingapparatus including injection molds and expansion molds each beingseparately closed by its own hydraulic or mechanical systems in suchmanner as to avoid the application of unequal closing forces on themolds. It is also an object of this invention to provide carrier meansfor the blow sticks which permit efficient transfer thereof between theinjection and expansion molds without employing a 360 rotatableturntable so as to avoid the usual problems of indexing the blow sticksand inherent problems of alignment thereof with the molds.

DESCRIPTION OF THE DRAWINGS The manner in which the objects of theinvention are FIG. 1 is a plan view taken through the horizontal centerline of the instant invention.

FIG. 2 is a side elevation view of the blow mold apparatus.

FIG. 3 is similar to FIG. 1 and depicts the position of the apparatus inits first stage or operation.

FIG. 4 depicts the apparatus in the second stage of its operation withthe blow sticks having been reciprocated.

FIG. 5 depicts the apparatus at the completion of stage two.

DETAILED DESCRIPTION As indicated in my copending application, apreferred process for obtaining an oriented plastic container at aneconomical production rate includes the injection of a plasticizedmaterial into a mold about a core, uniform cooling to within a fewdegrees of the materials glass transition temperature (T and expansionto form the finished article. In view of the relatively low thermalconductivity of the plastic, the cooling process involves two steps.First, the exposed surfaces are cooled to or below T through heattransfer to the core and the mold and then the parison is removed fromthe mold to a delay position such that the heat within the interior ofthe parison will flow to the exterior walls cooling the interior to Tand reheating the exposed surfaces so as to obtain a more uniformcross-section temperature. Accordingly, the instant invention includes astructural arrangement which facilitates the formation of a parison on acore, cooling, a transfer to a delay position with subsequent placementof the parison into a blow mold for expansion.

As illustrated in my preferred embodiment, the apparatus for efficientlypracticing the process may include an injection mold l0 and an expansionmold 20. As shown in FIG. 2, the expansion mold 20 may comprise an uppermold half 21 and a lower mold half 22 supported for vertical movement byguide rods 24. Hydraulic cylinders 25 and 26, interposed betweensupports 5 and 6, are then utilized for opening andclosing the molds.

Preferably disposed opposite of this expansion mold is an injection mold10 (FIG. 1) which also comprises upper and lower mold halves (the lowermold half 11 only being depicted) which are supported for verticalmovement by tie bars 12 upon actuation of hydraulic cylinders (notshown) similar to those utilized for the expansion mold 20. An injectionnozzle 60 of a thermoplastic extruder is stationed adjacent theinjection mold as depicted in FIG. 1 and is programmed to deliver aplasticized material into the mold through an aperture 14 upon closingof the mold.

Such material, upon injection into mold 10, forms a parison about anappropriate core 1, 2, 3 and 4 which are held by two core carriers 35Aand 35B supported for both rotational and rectilinear motion bycountershafts 31 and 32 upon a fixed shaft 30. The carriers 35A and 35Bcomprise two linear members extending radially away from a hub 34 atapart, and support at each end thereof arms A-l, A-2, and B-3 and B4 towhich are affixed cores or blow sticks I, 2, 3 and 4. Preferably, thehubs 34 are constrained for rotation with the countershafts, but mayreciprocate along their external surfaces as hereinafter described.

Double acting cylinders 40 and 41 are interposed between support arms 42and 43 of each countershaft 31 and 32 and the core carriers 35A and 358for obtaining reciprocal motion of the carriers so as to place theappropriate cores (1 and 2 or 3 and 4) in juxtaposition with the moldsupon opening and closing thereof. As depicted in FIG. 1, the hydraulicmotor 40 has placed the cores 1 and 2 of carrier 35A in juxtapositionwith the mold halves of the injection mold l and the blow mold 20. Uponopening of the mold halves by the hydraulic cylinders (25 and 26 for theblow mold), the motor 40 will reciprocate the carrier 35A to the leftfor cooling the parison (FIG. 4) while the carrier 35B and its cores 3and 4 are moved into juxtaposition with these two molds by the motor 41.

In addition to reciprocating the core sets 1 and 2 or 3 and 4 into andout of juxtaposition with the molds, means are provided for rotating theindividual core sets between the injection mold l0 and the expansionmold 20. Such means may take the form of two motors M-l and M2 Of thereversible, one-half revolution type whose pinion drives a gear 45constrained for rotation with its associated countershaft 31 or 32. Suchmotors and associated structure obviously will avoid the normal 360rotation of the cores, and thus alleviate substantial indexing problemsof the carriers, and facilitate the connection of hydraulic andpneumatic conduits to the cores and motors minimum sealing problems.Although not disclosed, simple indexing means in the form of abutmentsfor all of the hydraulic and electrical motors Ml and M2 may besufficient.

MODE OF OPERATION FIGS. 1, 3, 4 and 5 illustrate the steps through whichthis novel apparatus accomplishes the formation of a biaxially orientedhollow article. In FIG. 1, the cylinders 40 and 41 have reciprocated thecore carriers 35A and 358 to the right so as to place the cores 1 and 2of carrier A into the juxtaposition with the injection and the blowmolds and which were subsequently closed by hydraulic cylinders such asand 26 for the blow mold. In this stage of operation, the extruder willinject a thermoplastic material into mold 10 so as to form a parisonupon core 1 while a fluid is directed through a conduit 23 in arm A2 andthe core 2 so as to expand the parison formed upon this core against theinterior walls of the blow mold 20. Subsequently, the surfaces of theparison adjacent the core and the injection mold are cooled to or belowthe glass transition temperature of the material by fluid passingtherethrough as suggested in application, Ser. No. 201,823. Thus, core 1may remain in the injection mold 10 for the normal time of injection(approximately 3 seconds) and for an additional cooling period (4 ormore seconds). During this stage, ejector means 50 will first strip apreviously formed hollow article 51 from the core 4, and motor M-2 willrotate the countershaft 32 and its carrier 353 through 180. Thus,ejection of a hollow article 51 and rotation of the carrier 35B occurssimultaneously with the injection and blowing of parisons on cores 1 and2 of carrier 35A. Additionally, it should be noted that the parisonpreviously formed upon core 3 is exposed to the atmosphere during theinjection of the parison upon core 1, and this delay prior to theexpansion will permit heat to transfer from the interior of the parisonto the surfaces adjacent the core and that exposed to the atmosphere.Such delay in conjunction with the prior cooling will permit a moreuniform cross-section temperature near T to be obtained so as to achievemaximum orientation.

FIG. 3 depicts the completion of this stage of operation.

The next stage of operation is the opening of molds l0 and 20 andsubsequent reciprocation of carriers 35A and 35B and the cores to theleft by the motors 40 and 41 so as to place cores 3 and 4 injuxtaposition with the molds. Due to the prior rotation of carrier 35Bduring phase one, core 4 is now placed adjacent the injection mold andthe molds will be closed by the appropriate hydraulic motors (see FIG.2). Injection and cooling of a parison about core 4 will take placewhile the parison previously formed on core 3 is blown in the blow mold20. During this process of injection and blowing on the cores 3 and 4,the hollow article will be ejected form core 2 of carrier 35A which willthen be rotated 180 through actuation of the motor Ml. Subsequently, themolds will open and the carriers will be shifted for continued operationsuch that injection and expansion occurs with respect to the cores ofone carrier while the cooling, article ejection and rotation of theother cores takes place.

It should now be appreciated that through the utilization of twocarriers (each having at least two cores thereon) a parison formed uponone of the cores will be subjected to a delay and heat redistributioncycle during the injection of a parison onto a core of another carrier.It is this additional delay step which permits the formation of a hollowarticle 51 with additional strength characteristics. Such cooling asdescribed in this application and the subsequent expansion results inbiaxial orientation of the article. Additionally, by providing the twocarriers, the overall rate of producing the articles is not reduced.

The apparatus herein disclosed, including the utilization of separatehydraulic cylinders and four tie or guide bars for both the injectionmold and the blow mold, permits the application of the desired moldclosing forces without incurring the problem of unequal distribution ofstress on the two molds. Too, minimum frame structure is utilized forsupporting the molds. Additionally, it should be quite clear thatbyproviding two separate carriers for the cores, only l of rotation of thecarriers are necessary to transfer the cores from the injection mold tothe blow mold. Such minimum rotation alleviates prior problems withrespect to accurate indexing of a 360 turntable and at the same timepermits or facilitates less expensive means of connecting the air orfluid pressure conduits to the cores for blowing of the hollow articles.Alternatively, the utilization of a 360 turntable will result insubstantial sealing problems.

As previously indicated in the specification, there are numerousmodifications which may be made to my preferred embodiment. For example,it should be quite clear that the lower mold halves may be fixed withthe support shaft 50 being adapted for vertical movement so as to raisethe cores out of them.

In conjunction with these preferred embodiments, I claim:

1. An apparatus for making hollow articles comprising:

a. injection and blow mold units carried by a frame means and includingmeans for opening and closing same;

b. carrier means having an axis and multiple separate sets of coresspaced along said axis, said cores being receivable by the molds;

c. means for reciprocating said multiple sets of cores along said axisso as to place one set in juxtaposition with said mold units at a time;and

d. means for rotating the sets of cores about said axis between theinjection and blow mold units.

2. An apparatus as recited in claim 1 in which:

a. said carrier means are supported for reciprocable and rotationalmotion and a countershaft carried by a fixed elongated shaft extendingalong said axis.

3. An apparatus as recited in claim 1 together with:

a. motor means carried by the support for effecting individual rotationof the sets of cores.

4. An apparatus as recited in claim 1 in which:

a. said sets rotate less than 361 in transferring said cores between themolds.

5. An apparatus for making hollow articles comprising:

a. injection and expansion mold units supported about a carrier means;

b. means carried by a support for opening and closing said mold units;

c. carrier means mounted on a support between said mold units;

d. at least two separate sets of cores mounted on said carrier means;

e. means for reciprocating said carrier means along an axis extendingbetween said mold units to alternatively place the cores of one set injuxtaposition with said injection and expansion molds and the cores ofanother set at a delay position; and

. means for rotating said carrier means about said axis to alternate thecores between the injection and expansion molds.

6. An apparatus for forming hollow plastic articles comprising meansdefining a fixed axis, injection and expansion molds disposed along aline which extends transversely of said axis in any axially fixedposition, carrier means mounted for reciprocatory movement along androtary movement about said axis, two cores supported by said carriermeans and disposed along a line which extends transversely of said axisand in accordance with the relative positions of said molds forregistration in said molds, means for reciprocating said carrier meansalong said axis between a position wherein said cores are in registerwith said molds and a position axially offset from and clear of saidmolds, and means for rotating said carrier means about said axis foralternating said cores between each of said molds.

7. Apparatus as recited in claim 6 wherein said molds are split moldsand are movable transversely of said axis.

8. Apparatus as recited in claim 6 wherein said axis is defined by afixed shaft, and said carrier means are mounted on said shaft for thereciprocating and rotating movement thereof.

9. Apparatus as recited in claim 6 wherein said axis is defined by afixed shaft, and said carrier means are mounted on said shaft for thereciprocating and rotating movement thereof, said shaft extendingbetween said molds, said carrier means including a carrier mounted onsaid shaft on each side of said molds, and each carrier carrying a setof said cores for alternating cooperation with said molds.

10. The apparatus of claim 9 wherein said means for rotating saidcarrier means includes separate means for rotating each of said carriersindependently of one another.

1. An apparatus for making hollow articles comprising: a. injection andblow mold units carried by a frame means and including means for openingand closing same; b. carrier means having an axis and multiple separatesets of cores spaced along said axis, said cores being receivable by themolds; c. means for reciprocating said multiple sets of cores along saidaxis so as to place one set in juxtaposi-tion with said mold units at atime; and d. means for rotating the sets of cores about said axisbetween the injection and blow mold units.
 2. An apparatus as recited inclaim 1 in which: a. said carrier means are supported for reciprocableand rotational motion and a countershaft carried by a fixed elongatedshaft extending along said axis.
 3. An apparatus as recited in claim 1together with: a. motor means carried by the support for effectingindividual rotation of the sets of cores.
 4. An apparatus as recited inclaim 1 in which: a. said sets rotate less than 361* in transferringsaid cores between the molds.
 5. An apparatus for making hollow articlescomprising: a. injection and expansion mold units supported about acarrier means; b. means carried by a support for opening and closingsaid mold units; c. carrier means mounted on a support between said moldunits; d. at least two separate sets of Cores mounted on said carriermeans; e. means for reciprocating said carrier means along an axisextending between said mold units to alternatively place the cores ofone set in juxtaposition with said injection and expansion molds and thecores of another set at a delay position; and f. means for rotating saidcarrier means about said axis to alternate the cores between theinjection and expansion molds.
 6. An apparatus for forming hollowplastic articles comprising means defining a fixed axis, injection andexpansion molds disposed along a line which extends transversely of saidaxis in any axially fixed position, carrier means mounted forreciprocatory movement along and rotary movement about said axis, twocores supported by said carrier means and disposed along a line whichextends transversely of said axis and in accordance with the relativepositions of said molds for registration in said molds, means forreciprocating said carrier means along said axis between a positionwherein said cores are in register with said molds and a positionaxially offset from and clear of said molds, and means for rotating saidcarrier means about said axis for alternating said cores between each ofsaid molds.
 7. Apparatus as recited in claim 6 wherein said molds aresplit molds and are movable transversely of said axis.
 8. Apparatus asrecited in claim 6 wherein said axis is defined by a fixed shaft, andsaid carrier means are mounted on said shaft for the reciprocating androtating movement thereof.
 9. Apparatus as recited in claim 6 whereinsaid axis is defined by a fixed shaft, and said carrier means aremounted on said shaft for the reciprocating and rotating movementthereof, said shaft extending between said molds, said carrier meansincluding a carrier mounted on said shaft on each side of said molds,and each carrier carrying a set of said cores for alternatingcooperation with said molds.
 10. The apparatus of claim 9 wherein saidmeans for rotating said carrier means includes separate means forrotating each of said carriers independently of one another.